Feminine hygiene articles are used by women during their menstrual periods to receive and contain blood discharges from the vagina. In addition to collecting menses, these absorbent sanitary articles may also be used to protect the wearer's undergarment from other bodily fluids such as urine in the case of light incontinence of the user. These articles are generally flat and comprise a body-facing surface, an opposite garment-facing surface and absorbent structure, normally referred to as an absorbent core, placed in-between. The body-facing surface of the article is the first exposed to the flow of the bodily fluid, which is then absorbed and directed to the absorbent structure. The garment-facing side of the article normally comprises at least one fluid impermeable layer to prevent the fluid from leaking from the absorbent structure to the garment.
In the past, it was common for the body-facing surface of feminine hygiene articles to be entirely made of a liquid pervious topsheet that let or lead the fluid to the inner absorbent structure. More recently, so called “hybrid” topsheets have been proposed wherein a central acquisition layer is flanked by lateral outer layers of a different material. For example WO 93/09744 (Procter & Gamble) discloses an absorbent article with a nonwoven outer layer having an opening positioned in the central zone and apertured thermoplastic film layer positioned beneath the outer layer. This topsheet is said to be improving the feel and comfort of the user. U.S. Pat. No. 5,533,991 and EP 523,683 A1 (both to Kimberly-Clark) disclose absorbent articles which includes two different materials on the body-side cover.
However the components of these hybrid topsheets have only been proposed in a single shade, usually white. An exception to the traditional white products is found in WO 02/07662 (Procter & Gamble), where dark colored absorbent articles such as sanitary napkins or pantiliners are proposed. However the surface of these articles is entirely black and does not have the traditional white appearance that the consumer expects to find for feminine hygiene articles of this category. Hybrid topsheets having lateral zones of a shade which differs from the central zone have not been disclosed. In particular, it has not been proposed in the prior art to use colored (by colored we mean non-white) pigments in selected portions of the topsheet only, rather than the whole surface of the topsheet as in WO 02/07662.
Among the numerous attempts to improve the properties of sanitary articles, it has also been proposed to apply certain compositions on selected parts of the articles. For example WO 02/076339 (Paragon Trade Brands) discloses absorbent articles having hydrophobic leak protection zone on the body-facing surface of the article. The hydrophobic substance is preferably cocoa butter. WO 2004/060242A1 discloses feminine care products having a band of spaced apart deposits of a barrier substance material on the top cover. The bands are said to act as a fluid barrier against lateral flow of bodily fluids.
Although it has been proposed in the past to apply colored composition to lateral zones of the topsheet of absorbent articles, it remains technically difficult to apply or print a colored composition on absorbent of articles in a precise way, in particular if the color is applied in a pattern other than a straight line. This is at least because it may be difficult and costly to continuously monitor the high-speed production lines to detect and correct the inevitable displacement in the machine direction or in the machine transversal direction that may occur during printing, resulting in accidental misplacement of the composition when it is applied.
In another aspect of the ongoing development of absorbent articles, it has been proposed to use gradient cores instead of the traditional laminate cores. Gradient absorbing core materials (herein “gradient core”) are designed to quickly absorb fluid from the top of the core's surface to its bottom and then distribute in the horizontal plane direction. This is usually achieved by a unitary multistratum construction which is anisotropic in the vertical direction for fast fluid acquisition. The material stratum density and the average pore size decrease from top to the bottom of the core to drive the bodily fluid to the bottom of the core. A typical example of gradient core can be found in WO 0074620A1 (to BKI).
Although the intensity of the stain around the fluid impact zone (the aureole) at the surface of the core is lower in the so-called gradient cores than with traditional laminates cores or other absorbent structures, the stain sizes may by comparatively larger because the fluid is not uniformly propagated in the thickness of the core but concentrate in the bottom of the gradient core. It would be desirable to mask this increase in stain size when using gradient core.
Continual improvements in technology have led to absorbent products having excellent fluid absorption and retention properties. However some of the common problems still associated with these articles include leakage of the bodily fluids through the lateral edges of the articles and re-wetting of the body-facing surface. Re-wetting happens when bodily fluid already absorbed in the absorbent structure resurface, for example due to the pressure exerted on the core by the user's movement.
Furthermore, although the prior art has focused on leakage prevention and improved feel, there is still a need for absorbent articles with a better visual appearance. Before use, it would be beneficial to improve the appearance of absorbent articles in a way which is economical and practical. After use, it would be beneficial to mask or reduce the size of the stains on the body-facing surface of the articles.